1. Field of the Invention:
This invention relates to a device for propelling a pipe from a vertical shaft, and more particularly, to a device for exerting propelling power to small bore pipes such as water supply and drainage pipes, gas pipes and cable laying pipes to force them into the ground from the vertical shaft.
2. Description of the Prior Art:
Conventionally, a plurality of hydraulic jacks are used for a device for propelling pipes from vertical shafts. The respective hydraulic jacks forming a propelling device are provided to contact on one end a reacting shaft wall of the vertical shaft and on the other end the end of the pipe. The pipe in the vertical shaft is forced into the ground by the operation of the hydraulic jack.
Now, when on operative stroke of the hydraulic jack is made equal to or longer than the length of the pipe, the pipe can be forced from the interior to the exterior of the vertical shaft by only one operation of the hydraulic jack. On the other hand, since the length of the hydraulic jack has to be equal to or longer than that of the pipe, the size of the shaft, i.e., the distance between the reacting shaft wall and the shaft wall surface opposed thereto must be at least 2 times the length of the pipe.
Thus, a problem is encountered in a lot of labor and cost needed for forming the vertical shaft.
On the other hand, when on operative stroke of the hydraulic jack is shorter than the length of the pipe, the size of the vertical shaft can be made less than that in the case of said jack having the operative stroke equal to or longer than the length of the pipe. In this case, however, the pipe cannot be forced into the ground unless a strut is interposed between the pipe and the hydraulic jack. That is, the pipe must be propelled through said strut by extending a rod of the hydraulic jack to force a portion of the pipe into the ground and then withdraw the rod so that said strut is disposed between the pipe end and the rod end of each hydraulic jack to operate again the hydraulic jack. Depending upon the size of said operative stroke must be further reciprocated the rod and added another strut to force the pipe into the ground.
Thus, though the labor and cost needed for forming the vertical shaft can be reduced, troubleseome operations such as arrangement of a plurality of struts are added conversely. The efficiency of operation is then obliged to be degraded.
Also, a plurality of said conventional hydraulic jacks are arranged in the form of a box spaced from each other in the circumferential direction of the pipe between the pipe to be propelled and the reacting shaft wall. Thus, measuring instruments such as a propelling error measuring instrument applying laser to the measurement cannot be installed and operated on the pipe axis between the jacks so that troubles take place in measuring the propelling direction of the pipes sequentially forced into the ground to present problems that the operative space in the vertical shaft is narrowed or the vertical shaft must be expanded.